Experimental study and theoretical analysis of a Roto-Jet pump in small scale organic Rankine cycles

Highlights: • An experimental system for testing the pump in organic Rankine cycle was developed. • The performances of a Roto-Jet pump in organic Rankine cycle were obtained. • The cycle performances were investigated for every operation point of the pump. • The optimal operation points were found for different rotational speeds of the pump. • The strategy of adjusting the pump rotation speed was discussed. - Abstract: The organic Rankine cycle is one of the most promising methods for converting low grade heat into power. However, the technology of small scale organic Rankine cycle is not as mature as that of large scale system. One of the limiting factors is the circulation pump. In the present work, a simulative organic Rankine cycle condition was created for performance testing of the circulation pump, and the results of a Roto-Jet pump were obtained for different rotational speeds. On this basis, an examination of small scale organic Rankine cycle system has been carried out. The results show that the efficiency of the pump is between 11% and 23%. Increasing the rotational speed of the pump or reducing the flow rate leads to a general decrease of pump efficiency in the parametric ranges under study. It is also found that the pump is suitable for the small scale organic Rankine cycle systems with evaporating temperature between 99.5 °C and 127 °C, and the organic Rankine cycle system is suitable for converting the heat with available thermal power between 66.2 kW and 92.7 kW into power. In addition, the optimal operation points were found to correspond to highest organic Rankine cycle efficiency for different rotational speeds of the pump. Based on the results of optimal operation points, the strategy of adjusting the pump rotation speed and the effects of superheat were investigated.